1. Field of Invention:
This invention relates generally to a setting tool for driving an anchor having a shaped shank into a hole drilled in masonry, and more particularly to an automatic tool operatively coupled to a standard rotary-impact drill-hammer which acts to hammer the shank of the anchor into the hole so as to cause it to lodge securely therein.
2. Status of Prior Art:
It is frequently necessary to secure fixtures or other parts against the surface of masonry. The term "masonry" as used herein encompasses not only brickwork and concrete but all rigid, non-metallic structural materials such as stone and plaster. The conventional practice for this purpose is to make use of an anchor bolt assembly which includes an expansible shell that is caused to expand when the bolt is turned by a wrench or other torque-producing tool, the expanded shell gripping the wall of the hole to securely retain the bolt therein.
Quite apart from the fact that conventional anchor bolt assemblies are composed of two or more cooperating components and are relatively expensive to manufacture, are the difficulties often experienced in making installations with such assemblies.
On a major construction site, it is generally necessary to use literally hundreds or thousands of multi-piece anchor bolts to secure such items as suspended ceilings, soffits and wall studding, or to make similar attachments requiring repetitive anchor bolt operations. In each of these, the bolt must be properly inserted in the hole and then turned by a tool until the bolt is locked in the hole by its associated expansible shell. This requires a significant degree of care by the installer. A large number of failures arise from unqualified installers who fail to drill an accurate hole or to adequately torque the anchor bolt. Moreover, there is no way of knowing whether the anchor bolt is not holding properly until it fails in services, and this may have tragic consequences.
Apart from the problem of improper installation, is the fact that with existing multi-piece anchor bolts, the installation of each bolt is a time-consuming operation. Since at a given site, this operation must be repeated over and over again, the operator in the course of a working day is only able to install a limited number of anchor bolts. This adds substantially to construction site labor costs.
In order to reduce the time involved in installing anchor bolts, single piece anchors have been developed which are driven into pre-drilled masonry holes, thereby obviating the need to turn in an anchor bolt to expand a wedging shell. Thus, the patent to Nillson, U.S. Pat. No. 3,894,469, discloses a nail-like anchor which when hammered into a hole has a weakened portion that is deformed by this action to effect the desired wedging. The Gutshall U.S. Pat. No. 3,518,915 also shows a one-piece expandable anchor.
Also of prior art interest is the single piece anchor marketed under the trademark "Rawl Drive" by The Rawlplug Company, Inc., of New Rochelle, N.Y. This anchor has a resilient shank, an intermediate section of which is split into two half sections having a semi-circular cross-section. These are expanded in opposite directions in the plane of the split. The unsplit diameter of the shank is significantly smaller than the diameter of the masonry hole in which the anchor is to be installed, whereas the maximum diameter of the split section is somewhat greater than that of the hole.
When the ""Rawl Drive" anchor is driven into a hole drilled in masonry, the expanded half sections thereof are compressed inwardly and straightened out. But because of the resilience of the half-sections, they seek to resume their normal expanded shape, thereby imposing an anchoring force on the wall of the masonry hole on opposite sides thereof.
A practical drawback of the ""Rawl Drive" anchor is that the bulge created by the split and expanded half section has a maximum transverse dimension which is necessarily significantly greater than the diameter of the hole drilled in the masonry, and consequently is greater than the diameter of the mounting hole in the fixture to be attached to the masonry wall by the anchor bolt. Because a "Rawl Drive" anchor, before entering the masonry hole, must first pass through the mounting hole in the metal fixture, the use of conventional fixtures in conjuntion with "Rawl Drive" anchors is precluded. That is to say, one cannot use the "Rawl Drive " anchor with a fixture whose mounting hole has a diameter which corresponds to that of the drilled hole, which is usually the case, for the Rawl Drive anchor cannot go through this mounting hole.
The above-identified copending patent application discloses a one-piece anchor capable of being driven axially into a hole drilled in masonry to cause the inserted bolt to lodge securely therein to hold a fixture or other part against the masonry surface. The anchor is constituted by a pre-shaped shank formed of resilient material whose memory is such that when the shank is forcibly deformed it seeks to maintain its original shape, the shank being integral, with a drivable head and having a maximum cross section which does not substantially exceed the diameter of the hole.
The shank is pre-shaped to include at least one undulation which deviates from the longitudinal axis passing through the head to create a shank bend having a peak on one side of the shank and upper and lower bases on the other side thereof. When, therefore, the anchor is driven into the masonry hole, this force seeks to straighten out the bend, the resultant deformation thereof exerting outward pressures against large contact areas of the wall of the hole at the peak and at the bases, which multi-level pressures strongly resist axial withdrawal of the shank. This one-piece, pre-shaped anchor is now being marketed under the trademark SPIKE and will hereinafter be referred to by this mark.
Among the significant advantages of a SPIKE anchor are (a) ease of insertion to facilitate high-speed installations, (b) an assured multi-level gripping action when the anchor is fully inserted in the hole, (c) a tight attachment of the fixture or other part held against the masonry surface, (d) a high level of holding power due to relatively large contact surface areas, and (e) an ability to go through the mounting hole of a fixture whose diameter corresponds to that of the hole drilled in masonry.
In installing a one-piece anchor of the SPIKE or any other type, one must first drill a hole in the masonry and then hammer the anchor into the drilled hole. In drilling the hole in hard masonry, the conventional practice is to make use of a standard rotary-impact drill-hammer having a chuck which grips a drill bit having a carbide tip, for conventional drill bits are ineffective in this material. The drill-hammer serves not only to rotate the bit but also to reciprocate it axially, so that the rotating bit is periodically impacted at a rapid rate into the masonry to facilitate the drilling action. This drillhammer makes it possible to drill the required holes at high speed; and when at a given construction site hundreds or thousands of holes must be drilled in masonry, the drill-hammer effects a considerable saving in drilling time.
But what significantly slows down installation of anchors on a large scale is the need to hammer each anchor into a drilled hole. The use of manually-operated hammers for this purpose, when hundreds or thousands of anchors must be driven into drilled masonry holes, is not only a time consuming and labor intensive operation, but because of its energy requirements, the installer may reach a point of exhaustion in a fairly short period, for each anchor requires substantial effort to be driven into place.
Moreover, with a manually-operated hammer, the installer must exercise care to be sure that with each blow of the hammer he correctly strikes the head of the anchor; for should the installer mis-strike, he may inflict damage on the masonry region adjacent the hole.
While powered hammers, such as pneumatic hammers, are available which do not entail effort on the part of the user to effect a hammering action, these powered hammers must be manipulated by the installer to be sure that the hammer correctly strikes the head of the anchor. Should a mis-strike occur, the adjacent masonry region may be damaged.